Paramedic Jane Bramley said: "We're tied up, so the emergencies are stacking up, waiting for us to clear at hospital."

One report seen by BBC Look North health reporter Sharon Barbour highlights 126 "serious incidents" - delays over two hours - 71 of which were at UHND.

'Appalling process'

County Durham and Darlington NHS Trust medical director Chris Gray said UHND was designed for 30,000 annual attendances at A&E but was seeing 63,000.

"They [patients kept waiting] have an appalling process of care and for that we are very, very sorry," Prof Gray said.

'Something had to break'

By Sharon BarbourBBC Look North

It was becoming uncomfortably common; stories of dialling 999 and then a long wait for an ambulance. Some were up to 12 hours and some patients died while waiting.

I began to investigate what was going so wrong and contacted the ambulance service to see first-hand what was going on.

I joined paramedics on a relentless 12-hour shift, the pressures they said were so great "something had to break".

They told me reaching emergencies in eight minutes was impossible when the casualty was 30 miles away.

In the control room I heard stories of dispatch workers crying as 70 calls would stack up and they had no ambulances left to send.

I also discovered documents showing paramedics were being seriously delayed, with patients, by hospitals unable to cope with any more patients themselves.

The service boss said, without more money, they would only be able to save the lives they can and others would have to wait.

"Our staff are working very, very hard. They work way beyond their contracted hours, the same as the ambulance staff, but the stark reality is that the numbers who present at our front door are really challenging."

He said NEAS could share the workload more fairly.

"They know that they have ambulances waiting outside our hospital - and still they come," he added.

Hospital officials said they did not believe any patient had been harmed by delays but was investigating waits of more than two hours. They are looking at solutions such as reallocating staff and beds.

NEAS chief executive Simon Featherstone said they were working with the hospital.

"We have ongoing dialogue with Durham. We put an ambulance liaison officer, at crucial times, into their emergency department in order to help with the handover of ambulance patients into the acute hospital."

Sharon Barbour has seen documents showing hundreds of ambulance patients had to be diverted to other hospitals in the last few months.

Health watchdog the Care Quality Commission said there was a responsibility to meet "essential standards of quality and safety" and that it would take "appropriate action" if a provider fell short.

A representative said: "It is important that hospitals, commissioners and ambulance services work together to reduce turnaround times and prevent avoidable diverts."